Network interfaces allow connection of a variety of devices to one another through a network, with individual devices including a network interface controller or network interface card (NIC) providing a physical layer (PHY) interface to transmit and receive signals to or from the network. Modern Ethernet networks provide interconnection using twisted pair wiring with magnetic coupling according to various standards. FIG. 4 shows the magnetic coupling for an Ethernet network interface, in which a driver 400 transmits data to a primary winding 406 of a transformer 410. The transformer has a secondary winding 408 connected through an RJ-45 connector to a load resistance RL representing the Ethernet network impedance. The transmit driver 400 is presented with series impedances Rt 402a and 402b, where RT=RL/2 for a 1:1 transformer turns ratio. The most popular line driver for Ethernet is based on a current mode. For a current mode transmit driver 400, a center tap CT of the primary winding 406 is driven by a voltage source (not shown). As seen in FIG. 5, a current mode driver 500 includes a current source 502 driving a load 504b (RLOAD). However, current mode drivers suffer from low efficiency since half the current is wasted in the internal resistance 504a (RINT). In addition, current mode line drivers often require digital wave shaping (e.g., at higher frequency above 500 MHz) to meet harmonic distortion requirements in different modes. FIG. 6 shows a voltage mode driver 600 with a voltage source 602 and an internal resistance 6046a (RINT) to drive a load 606 (RLOAD). Although voltage mode drivers offer better efficiency than current mode drivers do, the required peak voltage swings are different for different Ethernet modes. Some examples of Ethernet standards or modes are 10Base-Te (energy efficient), 100Base-T and 1000Base-T. A table 412 in FIG. 4 shows peak differential voltage swing amounts for the output voltage Vo across the network load resistance RL for three different modes 1000Base-Te, 100Base-T, and 10Base-Te. For a voltage mode driver, the differential peak swing at the output Vol of the voltage driver 400 doubles the required load swing Vo, assuming RT=RL/2. Thus, a 3.6 volt supply voltage is needed for a true voltage mode driver in 10Base-Te mode. In contrast, 1000Base-T or 100Base-T mode requires 1V differential peak swing, and voltage mode drivers 400 can be powered by a 2V supply for these modes. For a voltage mode driver to work across these three modes, a minimum 3.6V supply is required, but this leads to excess power consumption for 1000Base-T mode operation. Thus, conventional current mode drivers 500 and voltage mode drivers 600 do not provide low power solutions for supporting a three 1000Base-Te, 100Base-T, and 10Base-Te Ethernet modes and these conventional driver architectures do not allow operation from a low voltage battery or other low voltage supply.